Prostheta Posted May 14, 2012 Report Share Posted May 14, 2012 Oh certainly, I couldn't agree more Mattia. In my opinion however, a keyed joint is not an effort in complexity or functionality it is a move towards repetitive manufacture where each joint can have its fitting tolerance made far tighter. From a manufacturing perspective, either removing the need for skilled assembly or reducing the time a skilled builder spends considering each joint is both time and money saved. By dropping the neck tenon's "key" say half a mm towards the mating heel face a degree of pressure between the two pieces would be possible, guaranteeing that there would be no gaps between them. Similar in theory to how drawboring a mortice and tenon increases the locking pressure of the visible mating faces I guess. Quote Link to comment Share on other sites More sharing options...
HuntinDoug Posted May 23, 2012 Report Share Posted May 23, 2012 My set neck joints are a "locking" dovetail of sorts... However, it's perpendicular to what you are suggesting Carl (I think). The taper of the neck makes the neck pocket a low degree dovetail. When I route the neck pocket it overlaps the neck pup route. The neck heel is 1.25" thick, which makes it deeper than the bottom of the pup route, creating a "stop" for the end of the heel to rest against. If routed correctly (a slightly undersized neck pocket), it creates an interference fit ensuring a nice tight fit. One major advantage is if I decide to add a slight angle to the neck( = or < 4 degrees), I can sand an angle on the bottom of the neck heel quickly by hand. Quote Link to comment Share on other sites More sharing options...
Prostheta Posted May 23, 2012 Report Share Posted May 23, 2012 I presume that your tenons are full width in that case? Do you need to adjust the angle of the rear face of the heel where it butts up to the body? I have quite a thing about the Gibson-esque tenons which leave a u-shaped contacting face around the tenon, and the extension of that being Taylor who recess that face into the body so they can hide angle changes when shimming. All very cool stuff. Quote Link to comment Share on other sites More sharing options...
HuntinDoug Posted May 23, 2012 Report Share Posted May 23, 2012 Do you need to adjust the angle of the rear face of the heel where it butts up to the body? Nope... With a 2 hum layout, the slight angle that is created on the end of the tenon is hidden in the bottom of the neck pup route. Once the heel is knotched out for the pup, the angle is so small it ends up being filled with glue. Quote Link to comment Share on other sites More sharing options...
Prostheta Posted May 23, 2012 Report Share Posted May 23, 2012 (edited) Oh, I meant this rear glueing face: If you change the neck angle, this needs adjusting also. Taylor shim these front and top to maintain wood contact whilst hiding the angle in recesses: Edited May 23, 2012 by Prostheta Quote Link to comment Share on other sites More sharing options...
HuntinDoug Posted May 23, 2012 Report Share Posted May 23, 2012 Oops...Looks like I'm talking apples (electric), and you are talking oranges (acoustic). Quote Link to comment Share on other sites More sharing options...
Prostheta Posted May 23, 2012 Report Share Posted May 23, 2012 Same idea though. This is Taylor's apple joint: Quote Link to comment Share on other sites More sharing options...
RestorationAD Posted May 24, 2012 Author Report Share Posted May 24, 2012 Fail to see the advantages. Quote Link to comment Share on other sites More sharing options...
Prostheta Posted May 24, 2012 Report Share Posted May 24, 2012 I love these engineered solutions. The neck angle can be set precisely with shims plus the shape aligns the neck very accurately. Engineering is an artform in itself including dialling in that precision through design and CNC work. I laugh when people say CNC has no beauty. Quote Link to comment Share on other sites More sharing options...
RestorationAD Posted June 23, 2012 Author Report Share Posted June 23, 2012 ARRRRGG!!!!! The machine jumped 2 inches to the left today during a simple body outline and ruined a gorgeous flamed padauk top. Man this is the worst thing every... I will post pictures later when I calm down. I can not understand what happened.... I have been using this code for months. Now the machine is out of wack when homed and it is off about 1.75 inches on the X. AAAAAAAGHGGHHGGG! Quote Link to comment Share on other sites More sharing options...
RestorationAD Posted June 24, 2012 Author Report Share Posted June 24, 2012 So it looks like the X servo motor is toast.... I ran a reference hole drilling gcode and the distance between the 2 points on the X axis is supposed to be 11.5 inches. The machine actually drilled the holes 10.5 inches apart. So if I home the machine what it thinks is 12.5,12.5,0 is off by a little more than an inch on the X. Quote Link to comment Share on other sites More sharing options...
HuntinDoug Posted June 25, 2012 Report Share Posted June 25, 2012 Don't panic yet. The motor may be ok. If it was a motor problem it would most likely be intermittent. Does your system have steppers, or servos? It may be more of a "track interference" type problem, or a bearing problem. That is the advantage of a closed loop system. If there is a coordinant problem, the machine shuts down before it scraps the part. If you cant figure it out by tonight...give me a call. PM me if you need my #. Quote Link to comment Share on other sites More sharing options...
MiKro Posted June 25, 2012 Report Share Posted June 25, 2012 Don't panic yet. The motor may be ok. If it was a motor problem it would most likely be intermittent. Does your system have steppers, or servos? It may be more of a "track interference" type problem, or a bearing problem. That is the advantage of a closed loop system. If there is a coordinant problem, the machine shuts down before it scraps the part. If you cant figure it out by tonight...give me a call. PM me if you need my #. If not bainding somewhere problem then it may be you are getting RF interference or loosing steps. First recalibrate that axis. So RF interference wil cuase problems a s well. Are yousing sheilded cables for yuor stepers? Also for your limit switches? Bridging the + and - on your limit switches at the controller board with 0.1uf caps, non electrolytic will stop the RF problems. these can be boughtfor Radioshack or most electronic stores for about 0.30cents each. Also check how hot thingsare getting. Steppers put out a lot of heat as well as what are the settiings for your drivers? If they are say max 3.0amps then they should be adjusted to about 2.8amps so they don't overheat. also do they have Heat sinks and a fan moving air over them? All of these things can cause these problems. Now that summer is here the shop temp can make these problems show up. I know , I've been there and have more tha one Tshirt Call Doug if needed or get my # from him and call me. Mike Also check all connections that have screw type binding. REtighten. excuse my typing have had a scotch or 3 Quote Link to comment Share on other sites More sharing options...
RestorationAD Posted June 27, 2012 Author Report Share Posted June 27, 2012 Mikro and Doug. You guys rock thanks for jumping in and giving me help! So I called Probotix support yesterday because I have a warranty and calmed down enough to use it. First off they are top rate. Called me back right at 5:00 and talked to me after hours. It only took a few minutes to really figure out the issue. He had me check the leadscrew ... leadscrews should not move when the machine is sitting still. However I was able to move the X axis by turning the brass coupling with my fingers. He said "Pull the motor... if it falls off in your hand it is a broken shaft" Sure enough I pulled the motor and it fell off in my hand. Shaft had sheered off right at the motor. It was making just enough contact to spin the X leadscrew. This is why it seemed to be losing steps.... Probotix are overnighting the new motor and I should have it today. Just in time for weekend work. Excellent service on their part. I had no clue how much I use the machine these days until Sunday when I felt I was working alone... Quote Link to comment Share on other sites More sharing options...
RestorationAD Posted June 27, 2012 Author Report Share Posted June 27, 2012 Mikro you bring up a good point I am going to have to get a fan for the CNC room as it gets pretty hot in there. Quote Link to comment Share on other sites More sharing options...
MiKro Posted June 27, 2012 Report Share Posted June 27, 2012 Mikro and Doug. You guys rock thanks for jumping in and giving me help! So I called Probotix support yesterday because I have a warranty and calmed down enough to use it. First off they are top rate. Called me back right at 5:00 and talked to me after hours. It only took a few minutes to really figure out the issue. He had me check the leadscrew ... leadscrews should not move when the machine is sitting still. However I was able to move the X axis by turning the brass coupling with my fingers. He said "Pull the motor... if it falls off in your hand it is a broken shaft" Sure enough I pulled the motor and it fell off in my hand. Shaft had sheered off right at the motor. It was making just enough contact to spin the X leadscrew. This is why it seemed to be losing steps.... Probotix are overnighting the new motor and I should have it today. Just in time for weekend work. Excellent service on their part. I had no clue how much I use the machine these days until Sunday when I felt I was working alone... Rad what are the couplers that you are using? If they are solid metal then this will cause a problem. If you have any offset in the shaft to the leadscrew then they will eventually break the shaft. Also you need to file a flat on the stepper shaft for the set screw as well as the leadscrew. If you could post a pic of the shaft and leadscrew coupling that would be great. I wold be willing to make you a set of couplers that will workif there is room for them to fit. They are made from UHMW and absorb the shock and allow for it to have ome less than 1.5degree off angle and not have a problem without adding any additional backlash. also I had forgotten you had probotix. Same as me. Yes they are good people and always willing to help. Mike Quote Link to comment Share on other sites More sharing options...
RestorationAD Posted June 27, 2012 Author Report Share Posted June 27, 2012 Rad what are the couplers that you are using? If they are solid metal then this will cause a problem. If you have any offset in the shaft to the leadscrew then they will eventually break the shaft. Also you need to file a flat on the stepper shaft for the set screw as well as the leadscrew. If you could post a pic of the shaft and leadscrew coupling that would be great. I wold be willing to make you a set of couplers that will workif there is room for them to fit. They are made from UHMW and absorb the shock and allow for it to have ome less than 1.5degree off angle and not have a problem without adding any additional backlash. also I had forgotten you had probotix. Same as me. Yes they are good people and always willing to help. Mike Yes it was a turnkey Probotix Comet. Nice machine... cheap but nice. Had I built my own I would understand it more. But it is not complicated except for the dual Y leadscrew. So the couplers are solid brass. Nothing special a sleeve with 2 set screws. One on the shaft of the motor and one on the leadscrew. I have a flatspot in the motor shaft for the set screw. The motors are mounted on poly spacers so technically if the new couplers were longer I could get new longer poly spacers. With the rigid coupler I could see were this is going to happen again under load... I will get some pictures up tonight if I can. It might be nice to have some better couplers. Let me know what specs you need and I will get them to you. We can talk compensation offline. I will need 3 of them... one for each Y and one for the X. I don't think I need one on the Z. Quote Link to comment Share on other sites More sharing options...
HuntinDoug Posted June 27, 2012 Report Share Posted June 27, 2012 Sounds like a design flaw of that machine. Every machine has at least one "quirk" like that. I'd keep my eye on the other axis' too. I found it interesting that the Probotix comet has 2 motors on the long axis... It seems like they would fight each other if they were not tuned perfectly. Here are the couplers on my new machine. They have an interference fit plastic sleeve that breaks if it is torqued over the design limit of the motor. They work well. My old machine was a belt drive. Quote Link to comment Share on other sites More sharing options...
RestorationAD Posted June 27, 2012 Author Report Share Posted June 27, 2012 Sounds like a design flaw of that machine. Every machine has at least one "quirk" like that. I'd keep my eye on the other axis' too. I found it interesting that the Probotix comet has 2 motors on the long axis... It seems like they would fight each other if they were not tuned perfectly. Here are the couplers on my new machine. They have an interference fit plastic sleeve that breaks if it is torqued over the design limit of the motor. They work well. My old machine was a belt drive. Were did you get those? They are pretty. Quote Link to comment Share on other sites More sharing options...
MiKro Posted June 27, 2012 Report Share Posted June 27, 2012 Those are buna N type couplers. Probotix sells them as well. http://www.probotix.com/mechanical_components/ Quote Link to comment Share on other sites More sharing options...
RestorationAD Posted June 29, 2012 Author Report Share Posted June 29, 2012 CNC Fixed. I installed new motor last night... I need to get some Buna N Type couplers though or this is going to happen again. Quote Link to comment Share on other sites More sharing options...
Bionic Machinist Posted June 29, 2012 Report Share Posted June 29, 2012 CNC Fixed. I installed new motor last night... I need to get some Buna N Type couplers though or this is going to happen again. You can get those at Mcmaster carr as well. Quote Link to comment Share on other sites More sharing options...
RestorationAD Posted July 3, 2012 Author Report Share Posted July 3, 2012 These are the pictures of the original damage when the motor broke. CNC Is fixed now. Reposted incase anyone missed it in S9_Continues.... And the destruction starts...AHHHHHH! I was on the other side of the shop when I heard the machine start making too much noise. I ran to shut it down...still a little late. Quote Link to comment Share on other sites More sharing options...
MiKro Posted July 3, 2012 Report Share Posted July 3, 2012 a coupler again? By the way it looks you have lost steps on an axis. Quote Link to comment Share on other sites More sharing options...
RestorationAD Posted July 3, 2012 Author Report Share Posted July 3, 2012 a coupler again? By the way it looks you have lost steps on an axis. No I was just posting pictures of the original problem... The CNC is running fine now. I am going to upgrade the couplers soon enough. Quote Link to comment Share on other sites More sharing options...
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